1. Field of the Invention
The present invention relates to the healing of wounds and, more particularly, but not by way of limitation, to an apparatus for closing wounds that is compact, self-contained, and includes a disposable wound fluids canister and a porous pad, which is biocompatible with the wound tissue to facilitate the healing of wounds, but does not adhere to the healing tissue.
2. Background Information
Wound closure involves epithelial and subcutaneous tissue adjacent to the wound migrating towards the center of the wound until it closes. Unfortunately, closure is difficult with large wounds or wounds that have become infected. In such wounds, a zone of stasis (i.e. an area in which localized swelling of tissue restricts the flow of blood to the tissues) forms near the surface of the wound. Without sufficient blood flow, the epithelial and subcutaneous tissues surrounding the wound not only receive diminished oxygen and nutrients, but are also less able to successfully fight bacterial infection and, thus are less able to close the wound naturally. Such wounds have presented difficulties to medical personnel for many years.
The most common technique for closing open wounds has been the use of sutures or staples. Although such mechanical closure techniques are widely practiced and often effective, they suffer a major disadvantage by providing tension on the skin tissue adjacent the wound. That is, the tensile force required to achieve closure using sutures or staples causes very high localized stresses at the suture or staple insertion point. Such stresses commonly result in the rupture of the tissue at those points, which can eventually cause dehiscence in wounds, providing additional tissue loss.
Moreover, some wounds harden and inflame to such a degree due to infection that closure by stapling or suturing is not feasible. Wounds not reparable by suturing or stapling generally require prolonged hospitalization with its attendant high cost, and major surgical procedures, such as grafts of surrounding tissues. Examples of wounds not readily treatable with staples or sutures include large, deep, open wounds; decubitus ulcers; ulcers resulting from chronic osteomyelitis; graft site wounds; and partial thickness burns that subsequently develop into full thickness burns. The use of skin grafts in these situations can result in the encapsulation of bacteria and other impurities.
The above problem is discussed in WO 93/09727 which proposes as a solution a procedure for draining the wound by applying a continuous negative pressure to the wound over an area sufficient to promote migration of epithelial and subcutaneous tissue toward the wound. Although WO 93/09727 deals in some detail with the clinical considerations of this kind of treatment, the apparatus described has certain practical shortcomings.
One problem with the apparatus described in the above prior document is that no means are disclosed for avoiding spread of infection from one patient to another or re-infection of the patient being treated. The pad in the wound drainage device can be modified with an antimicrobial agent, such as Neosporin, to limit the migration of bacteria through the pad and into the vacuum tubes and canister while negative air flow is engaged as well as into the patient when the air flow has been disengaged.
An objective is to have a pad that (a) is made from biocompatible material and (b) has sufficiently small pore size that granulation tissue does not migrate into the pad. Granulation tissue is a matrix of collagen, fibronectin and hyaluronic acid carrying microphages, fibroblasts and neovasculature that aids in healing. This objective may be accomplished by using a pad that (a) has a tissue compatible lubricious surface, (b) has a growth factor impregnated surface, (c) has a molecular graft on the pad surface, and/or (d) is antimicrobial.
The pad utilized in the wound drainage device can be formed by several different means with the ultimate goal of providing a vacuum compatible portion and a healing tissue compatible portion. It is known in the prior art that foam can be blown to form porous materials; however, it is not disclosed in the prior art that foam can be blown into a wound cavity to form a biocompatible porous pad which is both compatible with the healing tissue and compatible with the vacuum and negative air flow as in the present invention. It is known in the prior art that surgical dressings, such as teflon or rayon, are useful because they are compatible with healing tissue, but it is not disclosed in the prior art the use of porous surgical dressings in conjunction with a porous pad as in the present invention. It is known in the prior art that biocompatible substances such as Hydromers can be used as a coating material to increase lubricity and/or reduce pore size of pads; however, the prior art does not disclose the use of such substances to coat pads as used in the present invention. It is known in the prior art that antimicrobial agents can be used to deter bacterial growth; however, the prior art does not disclose the use of such agents in conjunction with the pad of the present invention.
It is a primary object of the present invention to provide a wound closure apparatus that closes wounds without stressing the surrounding skin.
It is another object of the present invention to render technology like that disclosed in WO 93/09727 in a convenient, compact and self-contained, efficient and economically feasible system.
It is a further object of the present invention to provide a wound closure apparatus that includes a removable and disposable wound fluids collection canister to protect the wound closure apparatus from contamination.
It is still a further object of the present invention to provide a wound closure apparatus which makes use of a porous pad with a smooth outer surface having pores of a diameter of approximately 100 microns or smaller so as to prevent skin regrowth therein.
It is another object of the present invention to provide a porous pad which can be used in conjunction with a wound closure apparatus which pad has a tissue compatible lubricious surface, has a growth factor impregnated surface, has a molecular grafted surface and/or is antimicrobial.
In accordance with the present invention, there is provided a therapeutic apparatus for stimulating healing of wounds, said apparatus including a housing that contains a vacuum pump and a chamber for holding a disposable wound drainage collection cannister. The cannister preferably resides within the chamber and connects at an outlet with the vacuum pump and at an inlet with a pad. The pad is of a porous, compliant material which works well for distributing gas pressure in the wound environment and which also complies with the negative air flow. The pad has a smooth outer surface that has pores close enough together so that the healing tissue will not grow into the pad. The pores on the outer surface of this pad less than one millimeter, normally in the approximate upper range of 100 microns (or less) in diameter in areas where the pad is in contact with the wound. The outer surface of the pad can consist of the outer portion of the pad itself, a material adhered to the pad, or a material placed over the pad. The pad is placed over the wound or pressed into the wound and adhesively secured thereto to create a sealed environment at the wound. The pad is designed such that when the pad is removed it does not disrupt the healing tissue. Thus, when the vacuum pump activates, it evacuates air from the canister and thence the wound environment, resulting in the application of negative pressure to the wound, which in turn tends to promote drainage of fluids flowing from the wound into the canister. After the canister is filled, it is removed from the chamber, disposed of, and replaced with another canister to continue therapy.